DESCRIPTION OF RELATED ART
There are several examples of redundancy designs being used in technologies in the prior art, for example, in the fields of electronics and circuit components, light source arrays, and row drivers for flat panel displays, including LCD displays. Some of these are described in the following references, all incorporated by reference herein:
U.S. Pat. No. 5,111,060, May 5, 1992, Asada, "Electronic circuit equipped with redundant or spare circuit elements for every circuit element"; PA0 U.S. Pat. No. 5,612,968, March 1997, Zah, "Redundant multi-wavelength light source array"; PA0 U.S. Pat. No. 5,619,223, Apr. 18, 1997, Lee et al., "Apparatus for increasing the effective yield of displays with integrated row select driver circuit"; PA0 "Flat Panel Manufacturing Costs", Third Edition, 1996, Stanford Resources, Inc., Chapter 3, pages 80-81, "Repair Systems".
U.S. Pat. No. 4,719,634, Jan. 12, 1988, Streifer et al., "Semiconductor Laser Array with Fault Tolerant Coupling".
Although the above references use redundancy designs, the problem surrounding redundancy designs to compensate for damaged optical devices in a manner which minimizes additional fabrication or manufacturing steps does not appear to have been addressed.
In addition, if one applies redundancy techniques known in other fields to systems incorporating optical guiding structures such as waveguides and waveguide combinations, there are additional considerations to contend with, for example the matter of attenuation or loss. The attenuation or loss is that experienced by the light as it travels through the waveguide, and as it scatters off non-smooth waveguide boundaries. This loss is generally attributable to three different mechanisms, scattering, absorption and radiation. Scattering loss results in redirection of guided optical light into radiation modes or other guided modes. Scattering can be caused by the roughness of waveguide boundaries, particulates, etc. Absorption loss is the conversion of the optical energy into the form of heat. Radiation losses are significant e.g. when waveguides are bent through a curve.
As with the manufacturing issues, loss issues also are not addressed adequately in the above-identified references with respect to optical waveguide structures.